An autopsy and other tests were pending Tuesday on a skull and bones believed to be human remains that were discovered Monday in a ravine in the Malibu area, authorities said.

The discovery sparked immediate speculation they could be remains of Mitrice Richardson, missing since last September.

The remains were discovered when state rangers were searching an abandoned marijuana farm in “treacherous terrain,” Steve Whitmore of the Los Angeles County Sheriff’s Department said.

Members of Richardson’s family and of another family concerned about their relative, a Boy Scout leader missing since several years ago in the same area, went to the Malibu-Lost Hills Station Monday night and met with Department of Coroner Assistant Chief Ed Winter, according to broadcast reports.

The area where the remains were found is in Malibu Creek State Park, Whitmore said.

Rangers were brought to the area by helicopter and had to hike the rest of the way to reach the grove.

Whitmore said he doubted the remains were those of Richardson, who was released from the sheriff’s Malibu-Lost Hills Station last September and never seen again.

The body was found “30 miles from the station through incredible terrain, just incredible terrain,” Whitmore said.